Fetal death in twins.

OBJECTIVE: To examine the pattern and prospective risk of intrauterine fetal death (IUFD) in twin pregnancy by chorionicity.

DESIGN: Retrospective cohort analysis.

SETTING: Large national tertiary referral center.

POPULATION: All consecutive twin deliveries (1997-2006) ≥24 weeks.

METHODS: Retrospective review of all consecutive twin deliveries over 10 years to identify patterns of IUFD in twins and calculate gestation-specific prospective risks of IUFD. Fetal death was defined as intrauterine demise of a fetus ≥24weeks, intertwin birthweight discordance as ≥20% difference and growth restriction as birthweight <5(th) centile. Chorionicity was confirmed by postnatal placental examination.

MAIN OUTCOME MEASURES: Fetal death.

RESULTS: 1094 twin pairs including 276 monochorionic-diamniotic (MCDA) (25.3%) and 818 dichorionic-diamniotic (DCDA) twin pregnancies (74.7%) were studied. Twenty-nine fetal deaths occurred affecting 22 twin pregnancies. The incidence of IUFD (death of one or both fetuses) in MCDA twin pregnancies was three times that in DCDA pregnancies [11/276 (3.9)% vs. 11/818 (1.3%) p<0.001]. The majority of deaths in MCDA twins were associated with twin-twin transfusion syndrome (TTTS) prior to 30 weeks. In normally grown twins the prospective risk of IUFD was similarly low in MCDA and DCDA pregnancies after 34 weeks but in pregnancies complicated by abnormal growth, the prospective risk of IUFD was 3.4 in MCDA and 2.0 in DCDA pregnancies.

CONCLUSION: Twin pregnancies complicated by growth restriction or growth discordance were associated with a high risk of IUFD, particularly in affected MCDA twins. Conversely, in normally grown twins the risk was similarly low in MCDA and DCDA pregnancies after 34 weeks.